Well the the issue might be that
<A> your not properly maintaining you pc, clean and defrag it, blow out the dust once a month, heat issue are the root of a lot of evil in computers, you would be surprised how often I find a dust layer in a pc that looks more like a carpet then dust. and also make sure your keeping your pc free of virus's and what not, AVG free is a good program, or get kapersky if you don't mind investing in your computers safety, also, Threatfire works great combined with any anit virus software out there, is totally free, and also protects against key loggers. I wont give you any links, because everything I mentioned is easily found with google.
<B> drivers may need to be updated, or maybe even downgraded in some cases, just because a driver is new, doesn't mean its going to work with everything yet, I have sometimes had to roll back to a previous driver to fix things.
<C> what is your pc running in the background while you play? in general it is best to turn everything off not need to play a MMO, while running the game, shut all that off before you log in, also make sure your anti virus scanner isn't doing a scan or that windows update isn't running when your in game. <Facebook and myspace can lag games out very bad sometimes if you have them on while playing>.
As far as registry cleaners and editors go, Please, don't use them unless you understand the registry, I deal with this issue all the time, and have to fix computers where people have done stuff with their registry they shouldn't have because of those kinds of programs, They are good programs, and they do a lot of good sometimes, AS LONG as you know how to use them and understand the registry. otherwise, stick to defrag. heh
one more thing, If you find out how to fix a issue, post what the issue was, and how you fixed it, you might be able to save someone else a lot of grief and time by doing so, and its the "nice thing" to do.
EDITED TO SAY ~ and one more thing, shut your computer off every once in a while, a lot of programs and games have memory leaks, and sometimes a good old restart or shutdown and over night rest for your pc can do worlds of good. Personally I shut mine down at least every other, if not every day. and it keeps me happy